Greg Whatley Greg Whatley - 13 days ago 5
C# Question

UIApplication Assertion Failure in Xamarin.iOS App

I was in the middle of developing an update to my Xamarin Forms app, but when I debugged it on my iPhone, it crashed immediately on startup with the following message:

Assertion failure in -[UIApplication_runWithMainScene:transitionContext:completion:], /BuildRoot/Library/Caches/com/apple.xbs/Source/UIKit/UIKit-3600.5.2/UIApplication.m:3679

It was previously working fine, but now I can't run the app on my phone anymore without this crash. I have rebuilt several times and deployed from different computers, but nothing helps. How do I fix this issue?


Before this started occurring, I had made some additions to the code. Unfortunately, after removing all of my changes, this issue is still plaguing further development. Any help or resource that might lead me to a solution will be greatly appreciated.


After some deep searching, it turnes out that I mistakenly removed a part of my Application's constructor that initialized the MainPage. As a result, MainPage remained null. The framework probably tried to call a method or access a property without checking if the reference was null, causing the error. I'm not sure how long that mistake has been there.